package j20251023;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket=null;
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动！");
        DatagramPacket requestPacket=new DatagramPacket(new byte[4096], 4096);
        while(true){
            //1.接收请求并解析
            socket.receive(requestPacket);
            String request=new String(requestPacket.getData(),
                    0,requestPacket.getLength());
            //2.根据请求，计算响应
            String response=process(request);
            //3.将响应返回给客户端
            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),
                    response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            //4.打印一个日志
            System.out.printf("[%s:%d] req:%s resp:%s\n",requestPacket.getAddress(),requestPacket.getPort()
                    ,request,response);
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server=new UdpEchoServer(9090);
        server.start();
    }
}
